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<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">Hi John,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">we have seen crashes when running SPEC jbb2013 on linux x86_64 with the following options (with our SAPJVM):<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">-XX:+UseCompressedOops -Xms8192m -Xmx8192m -Xmn1600m -XX:+UseG1GC -XX:SurvivorRatio=4<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">With these options, our VM uses zero based compressed oops (shift 3).<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">It crashed with SIGSEGV:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># SIGSEGV (0xb) at pc=0x000000004a4c2e00, pid=1961, tid=140227895330560<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># accessing faulting address: 0x000000004a4c2e00<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">#<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># JRE version: 7.0_21<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># Java VM: SAP Java Server VM (7.1.130414 23.5-b02 Apr 14 2013 19:29:41 - dev - optU - linux amd64 - 6 - bas2:193987
(mixed mode) compressed oops)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># Problematic frame:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"># C 0x000000004a4c2e00 (sp=0x00007f8959e37ad8) (pc=0x000000004a4c2e00)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">The same test is passing since we fixed this issue.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE">Martin<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New";color:windowtext;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:DE">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:DE">
John Cuthbertson [mailto:john.cuthbertson@oracle.com] <br>
<b>Sent:</b> Mittwoch, 17. April 2013 01:42<br>
<b>To:</b> Doerr, Martin<br>
<b>Cc:</b> hotspot-gc-dev@openjdk.java.net<br>
<b>Subject:</b> Re: RFR (S): G1: Fix bug with compressed oops on x86_64 and sparc<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Martin,<br>
<br>
This looks good to me. Coleen has also reviewed the change and given it the thumbs up. I'll let you get back to me regarding a test case before pushing the changes.<br>
<br>
JohnC<o:p></o:p></p>
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<p class="MsoNormal">On 4/16/2013 1:38 AM, Doerr, Martin wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US">we found a G1 bug i</span><span lang="EN-US" style="mso-fareast-language:DE">n the template interpreter on x86_64 and sparc with compressed Oops.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">“do_oop_store” performs a “</span><span lang="EN-US" style="background:silver;mso-highlight:silver">store_heap_oop</span><span lang="EN-US">” which compresses the input register.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US">This compressed Oop is passed to the succeeding
</span><span lang="EN-US" style="mso-fareast-language:DE">g1_write_barrier_post, which is wrong.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">Correctly, g1_write_barrier_post needs the uncompressed Oop for the heap region crossing check.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">This fix preserves the uncompressed Oop in a register which gets passed to the g1_write_barrier_post:</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE"><a href="http://cr.openjdk.java.net/%7Egoetz/webrevs/g1-cOops_bug/">http://cr.openjdk.java.net/~goetz/webrevs/g1-cOops_bug/</a></span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">Please supply a bug id and review this change.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">Kind regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE">Martin</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:DE"> </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif";mso-fareast-language:DE"><o:p> </o:p></span></p>
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